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MattermostApplication

CVE-2023-5969

MEDIUM · 5.3 CVSS v3.1 Published 2023-11-06
Fix available
A fix is available. Upgrade to after 8.1.2 or later.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Mattermost fails to properly sanitize the request to /api/v4/redirect_location allowing an attacker, sending a specially crafted request to /api/v4/redirect_location, to fill up the memory due to caching large items.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

Mattermost's /api/v4/redirect_location endpoint does not properly sanitize requests, allowing attackers to send specially crafted requests that cause excessive memory consumption through caching of large items. This leads to a denial-of-service condition due to memory exhaustion.

MitigationImplement input validation and size limits on the /api/v4/redirect_location endpoint, and configure cache size constraints to prevent unbounded memory growth from large cached items.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
MattermostApplication
Affected:<= 7.8.11>= 8.0.0, <= 8.0.3>= 8.1.0, <= 8.1.2= 9.0.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Mattermost installation and version
    Run 'mattermost version' or check the Mattermost server logs/version endpoint. On Linux, also check /opt/mattermost/version.txt or the package manager. Look for the version string in the server response headers at the root URL.
    Affected if The installed version matches <= 7.8.11, 8.0.0-8.0.3, 8.1.0-8.1.2, or exactly 9.0.0
  2. Verify the /api/v4/redirect_location endpoint exists
    Send a GET request to https://your-server/api/v4/redirect_location?url=https://example.com (replace with your Mattermost URL). A 200 or 30x response indicates the endpoint is active.
    Affected if The endpoint responds, meaning the vulnerable code path is available
  3. Check if the endpoint accepts arbitrary URLs without size limits
    Send requests to /api/v4/redirect_location with increasingly large URL parameters (e.g., URL strings >10KB). Observe if responses are cached and returned successfully.
    Affected if Large URL parameters are accepted and cached without rejection or size limits being enforced
  4. Monitor memory usage during endpoint access
    Observe Mattermost server memory consumption (via 'top', 'htop', or system monitoring tools) while making repeated requests to /api/v4/redirect_location with various URL parameters.
    Affected if Memory usage grows unbounded as the endpoint is accessed, indicating unbounded caching is occurring

You are affected if your Mattermost version falls within the vulnerable ranges AND the /api/v4/redirect_location endpoint is accessible, as this allows unbounded caching leading to memory exhaustion.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 8.1.2
Interim mitigation

Implement input validation and size limits on the /api/v4/redirect_location endpoint, and configure cache size constraints to prevent unbounded memory growth from large cached items.

Recommended fix Moderate confidence

Mattermost 9.0.1 or later (or the latest stable 7.x/8.x patch for your branch)

  1. 1. Back up your Mattermost database and configuration files.
  2. 2. Identify your current Mattermost version by checking the System Console > About page.
  3. 3. For Mattermost 7.x versions (≤7.8.11): Upgrade to version 7.8.12 or later.
  4. 4. For Mattermost 8.0.x versions (≤8.0.3): Upgrade to version 8.0.4 or later.
  5. 5. For Mattermost 8.1.x versions (≤8.1.2): Upgrade to version 8.1.3 or later.
  6. 6. For Mattermost 9.0.0: Upgrade to version 9.0.1 or later (recommended: latest 9.x stable release).
  7. 7. After upgrade, verify the /api/v4/redirect_location endpoint functions correctly.
  8. 8. Monitor server memory usage to confirm the memory exhaustion issue is resolved.
Caveat Review Mattermost release notes for your target version for any breaking changes, especially when upgrading across major versions (e.g., 7.x to 8.x to 9.x)

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Mattermost Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-5969 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data